The present invention relates in general to substrate manufacturing technologies and in particular to an apparatus for servicing a plasma processing system with a robot.
In the processing of a substrate, e.g., a semiconductor wafer or a glass panel such as one used in flat panel display manufacturing, plasma is often employed. As part of the processing of a substrate (chemical vapor deposition, plasma enhanced chemical vapor deposition, physical vapor deposition, etc.) for example, the substrate is divided into a plurality of dies, or rectangular areas, each of which will become an integrated circuit. The substrate is then processed in a series of steps in which materials are selectively removed (etching) and deposited (deposition) in order to form electrical components thereon.
In an exemplary plasma process, a substrate is coated with a thin film of hardened emulsion (such as a photoresist mask) prior to etching. Areas of the hardened emulsion are then selectively removed, causing parts of the underlying layer to become exposed. The substrate is then placed in a plasma processing chamber on a substrate support structure comprising a mono-polar or bi-polar clamping electrode, called a chuck. Appropriate etchant source gases (e.g., C4F8, C4F6, CHF3, CH2F3, CF4, CH3F, C2F4, N2, O2, Ar, Xe, He, H2, NH3, SF6, SO2, BCl3, Cl2, SiCl4 etc.) are then flowed into the chamber and struck to form a plasma to etch exposed areas of the substrate.
However, in the normal course of operation, a plasma processing system may need to be serviced with a set of pre-defined service procedures. For example, the plasma chamber may need to be cleaned, or a plasma chamber part may need to be removed, placed, or aligned. In addition, servicing a plasma processing system may also expose an operator to hazardous duty (i.e., exposure to toxic gases or high temperatures, lifting heavy parts, etc.).
For example, pollutants or byproducts that are detrimental to the substrate may need to be cleaned from plasma chamber surfaces. Generally, volatile byproducts may be easily removed from the plasma chamber by a vacuum system, and hence tend to be less problematic. However, non-volatile byproducts will tend to be deposited on exposed surfaces within the plasma chamber or in the vacuum system. Comprised of organic and inorganic byproducts, these non-volatile byproducts are commonly generated from materials in the etchant gases (e.g., carbon, fluorine, hydrogen, nitrogen, oxygen, argon, xenon, silicon, boron, chlorine, etc.) and from materials in the substrate (e.g. photoresist, silicon, oxygen, nitrogen, aluminum, titanium, copper, platinum, iridium, iron, nickel, tantalum, etc.).
In addition, as physical structures within the chamber (e.g., chuck, chamber walls, etc.) are exposed to the plasma, they also tend to produce additional non-volatile byproducts either from their major constituents or impurities in their structure (e.g., aluminum, nickel, iron, tantalum, yttrium, silicon, carbon, titanium, magnesium, manganese etc.). For example, some components, such as the chuck, may become substantially etched in the process by which pollutants are partially and quickly cleaned from the plasma processing system, by striking the plasma without the substrate in a process called waferless auto clean or WAC. Repeated plasma exposure tends to physically alter structures, such as by surface chemical composition, morphology, physical dimensions, etc. In each case, these eroding atoms typically are volatile and pumped away or redeposit elsewhere in the chamber or on the substrate.
The degree of deposit adhesion to surfaces within the chamber, and hence the subsequent degree of potential contamination, is usually dependent on the specific plasma processing recipe (e.g., chemistry, power, and temperature), the specific operating procedure of the non-processing steps (e.g., substrate transfer methods, vacuum system transitions, periodic in situ cleans etc.), the geometry of the system and substrate components and the initial surface condition of chamber process kits. In general, organic bonds tend to be very strong and adhesive (i.e., C—H, C—C, C═C, C—O, C—N, etc.), since cross-linked relatively stable strictures are created. The addition of metallic atoms from any of the sources mentioned above will often exacerbate the cleaning problem by formation of metallic, metal-organic compounds or metal oxides or mixtures thereof. In addition, when these non-volatile byproducts eventually flake, they may subsequently increase the susceptibility of substrate defects, reduce the mean time between cleaning (MTBC), reduce yield, lead to unacceptable atomic surface contamination on the substrate, etc. For example, depending on the plasma process, conductive film of byproducts may form on plasma chamber interior surfaces which may impact the FW coupling of the plasma source and bias.
In operation, since substantially removing the byproducts may be time consuming, a plasma chamber is generally substantially cleaned only when, or preferably just before, particle contamination levels reach unacceptable levels, when the plasma processing system must be opened to replace a consumable structure (e.g., edge ring, optical access windows, etc.), or as part of scheduled preventive maintenance (PM). In general, experience has shown that servicing plasma processing equipment on a scheduled basis minimizes unscheduled downtime, smoothes production scheduling, improves yields, and extends the intervals between servicing.
In a typical preventive maintenance that includes a set of pre-defined service procedures, the plasma chamber is opened by an operator, wherein structures such as chamber walls, shields, gas distribution rings, showerheads, substrate support assemblies, robotic arms, and other accessible hardware may be either manually cleaned in place by the operator, or removed and replaced with a clean set of components.
Removable plasma chamber components (i.e., chuck, quartz ring, etc.) are often transported to a cleaning station somewhere else in the fabrication facility. Non-removable components (i.e., chamber walls, etc.) by definition cannot be removed, and hence must be physically cleaned at the plasma processing equipment location.
In a typical cleaning process, chamber components are exposed to various cleaning solutions and physically rubbed with a cleaning object (i.e., a sealed-border knitted polyester wiper, an abrasive pad, etc.) in order to remove deposit adhesion. In a common technique, the removable component is exposed to a solution comprising an oxidizer, such as H2O2 and ly rubbed to loosen by-product deposits. The removable component is then rinsed with DI (de-ionized) water, and dried by a filtered inert gas, such as nitrogen. The structure is then ultrasonically cleaned with a keytone reagent, such as acetone, and again periodically rubbed.
Since much of the cleaning process is manual, the effectiveness of the clean is directly related to the skill of the cleaning technician, and the degree to which the technician adheres to the vendor recommended cleaning process. The vendor, having designed the plasma process system, and being aware of stringent part specifications, is generally in the best position to determine the optimum cleaning technique for a given manufacturing process. For example, part specifications may include the material properties of a part in relationship with another part or process parameter, the shape of the part, the power deposition profile between a set of parts for a given period of time, the location of a part within the plasma chamber, the expected wear of the part, temperature and temperature transients, etc.
However, customers may become complacent, or may instead only focus on maximizing equipment production time, and not on the performance of a thorough cleaning, which may amount to many thousands of dollars per hour in lost production time. For examples, operators who are not properly monitored can create problems by modifying the cleaning method, such as by eliminating steps, doing a less than thorough job in cleaning deposit adhesion or attempting to improve the procedure without verifying compatibility or effectiveness with the recommended processes. Subsequently, incomplete or incompatible cleaning can cause the plasma processing system to fail particle checks during substrate processing re-qualification or after processing has resumed, requiring additional unplanned maintenance and downtime.
In view of the foregoing, there are desired an apparatus for servicing a plasma processing system with a robot.